This invention relates to materials and methods for detecting biomolecules in samples, and more particularly to a particulate solid phase having for encoding information concerning the assay, and to assays employing such a solid phase.
Solid phase assays have been used to determine the presence and/or the concentration of biomolecules, such as proteins, peptides, nucleic acids, carbohydrates and lipids. Solid-phase assays can be performed in a variety of fluids, e.g., simple buffers, biological fluids, such as blood, serum, plasma, saliva, urine, tissue homogenates, and many others.
In solid phase assays, small beads, or microparticles, are typically used as the solid phase to capture the analyte. Solid phase microparticles can be made of a variety of materials, such as glass, plastic or latex, depending on the particular application. Some solid phase particles are made of ferromagnetic materials to facilitate their separation from complex suspensions or mixtures.
In conventional solid-phase assays, the solid phase mainly aids in separating biomolecules that bind to the solid phase from molecules that do not bind to the solid phase. Separation can be facilitated by gravity, centrifugation, filtration, magnetism, immobilization of molecules onto the surface of the vessel, etc. The separation may be performed either in a single step in the assay or, more often, in multiple steps.
Often, it is desirable to perform two or more different assays on the same sample, in a single vessel and at about the same time. Such assays are known in the art as multiplex assays. Multiplex assays are performed to determine simultaneously the presence or concentration of more than one molecule in the sample being analyzed, or alternatively, to evaluate several characteristics of a single molecule, such as, the presence of several epitopes on a single protein molecule.
One problem with conventional multiplex assays is that they typically cannot detect more than more than about five analytes simultaneously, because of difficulties with simultaneous detection and differentiation of more than about five analytes. In other words, the number of different analytes that may be assayed simultaneously is limited by the solid phase.
This invention overcomes many of these problems by the use of transponders associated with the solid phase beads to index the particles constituting the solid phase. Thus, each individual transponder-containing solid phase particle can be assigned a unique index number, electronically encoded inside the particle, that can be retrieved by the scanner device at any time, e.g., at one time during the assay, at multiple times during the assay, or continuously during the assay. The index number may relate to the time and date on which the assay was performed, the patient""s name, a code identifying the type of the assay, catalog numbers of reagents used in the assay, or data describing the progress of the assay, such as temperature during different steps of the assay.
In an electronically-indexed multiplex assay of this invention, two or more transponders, each encoded with a different index number and constructed to bind a different analyte, are incubated with the sample in a single vessel. After necessary additions, incubations and washes are performed, which are similar to incubations and washes in existing assays, the solid phase is analyzed to detect a label indicative of binding of the analyte to the solid phase, such as fluorescence, color, radioactivity or the like. Solid phase analysis is either preceded or followed by the decoding of the index number on the transponder.
Determination of the label and decoding of the memory of the transponder can be done manually on two different instruments, such as a fluorometer and a dedicated scanner, although a single automated instrument that would perform both functions may be used. Such an instrument can be a modified fluorometer in which the scanner is mounted in the proximity of the fluorometer readout window, and reading the sample fluorescence and decoding the transponder are coordinated by a central computer. In addition, such an instrument can be equipped with an automated transport system for transponders.
In one aspect, the present invention provides an electronically-indexed solid phase particle for use in solid phase assays for biomolecules, comprising a transponder and a member of a biomolecular binding pair attached to the transponder.
In another aspect, the present invention provides a method of detecting biomolecules in a sample using solid phase particles having transponders.
In another aspect, the present invention includes a kit for detecting biomolecules in a sample using transponders, comprising assay vessels, a probe reagent, and a labelled conjugate reagent.